No tsunami threat was issued after the quake struck off Sarangani province on the main southern island of Mindanao at a depth of 78 kilometres (48 miles) at 0814 GMT, the USGS said in a statement.
There were no immediate reports of casualties but the quake was felt across a wide area of the mountainous island.
"I think it was the strongest earthquake I've ever experienced," Keeshia Leyran, 27, told AFP from Davao City, about 200 kilometres from the epicentre, where she was attending a conference.
"People around me were panicking and running to go outside. There are hundreds of people here at the event, so I was more scared of a stampede happening to be honest."
Quakes are a daily occurrence in the Philippines, which sits along the Pacific "Ring of Fire", an arc of intense seismic as well as volcanic activity that stretches from Japan through Southeast Asia and across the Pacific basin.
Agence France-Presse
Reader Comments
to our Newsletter